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TARG(4) FreeBSD Kernel Interfaces Manual TARG(4)
NAMEtarg - SCSI target emulator driver
SYNOPSISdevicetargDESCRIPTION
The targ driver provides an interface for usermode programs to emulate
SCSI target devices. A sample program that emulates a disk drive
(similar to da(4)) can be found in /usr/share/examples/scsi_target.
The targ driver supplies control devices, /dev/targ0, /dev/targ1, etc.
If a device is already in use, the open will fail and errno will be set
to EBUSY. After opening the device, the file descriptor must be bound to
a specific bus/target/LUN and enabled to process CCBs using the
TARGIOCENABLE ioctl. The process then uses write(2) to send CCBs to the
SIM and poll(2) or kqueue(2) to see if responses are ready. Pointers to
completed CCBs are returned via read(2). Any data transfers requested by
the user CCBs are done via zero-copy IO.
IOCTLS
The following ioctl(2) calls are defined in the header file
<cam/scsi/scsi_targetio.h>.
TARGIOCENABLE (structioc_enable_lun) Enable target mode on the LUN
specified by the following structure:
struct ioc_enable_lun {
path_id_t path_id;
target_id_t target_id;
lun_id_t lun_id;
int grp6_len;
int grp7_len;
};
The selected path (bus), target, and LUN must not
already be in use or EADDRINUSE is returned. If
grp6_len or grp7_len are non-zero, reception of
vendor-specific commands is enabled.
TARGIOCDISABLE Disable target mode and abort all pending CCBs. The
CCBs may optionally be read as they complete.
TARGIOCENABLE can then be called to activate a
different LUN. Multiple disable calls have no
effect. The close(2) system call automatically
disables target mode if enabled.
TARGIOCDEBUG (int) Enables CAM_PERIPH debugging if the argument is
non-zero, otherwise disables it.
FILES
<cam/scsi/scsi_targetio.h> describes the usermode interface.
/sys/cam/scsi/scsi_target.c is the driver source file.
/dev/targ* are the control devices.
SEE ALSO/usr/share/examples/scsi_target, scsi(4)FreeBSDTargetInformation, http://www.root.org/~nate/freebsd/.BUGS
Currently, only the ahc(4) driver fully supports target mode. The isp(4)
and sym(4) drivers have some target mode support but are untested.
The ahc(4) driver does not support tagged queuing in target mode.
AUTHORS
The targ driver first appeared in FreeBSD 3.0 and was written by Justin
T. Gibbs. It was rewritten for FreeBSD 5.0 by Nate Lawson
<nate@root.org>.
FreeBSD 11.0-PRERELEASE November 15, 2002 FreeBSD 11.0-PRERELEASE